Geometrical tool



Patented Oct. 18, 1921.

Qwmrhatoaa closed in Patent UNITED STATES PATENT OFFICE.

JAMES H. ROBERTS, OF CHARLESTON, SOUTH CAROLINA.

GEOMETRICAL TOOL.

Application filed January 3, 1921.

T 0 all whom it may concern:

Be it known that I, JAMES H. ROBERTS, a citizen of the United States, residing at Charleston, in the county of Charleston and State of South Carolina, have invented a new and useful Geometrical Tool, of which the following is a specification.

This invention relates to a geometrical tool of the same eneral type as that dis 0. 1,243,343 issued to me on Oct. 16, 1917, one of its objects being to provide a tool of this character having all of the advantages present in the patented device but which does not require the use of a graduated segment extending through more than 90.

A further object is to provide a tool of this character utilizing adjustable graduated blades or arms which are normally disposed at right angles to each other and which are adjustable angularly as one body relative to the main or stationary arm of the tool, one of the movable arms having an index readable in connection with the graduations on the segment.

A still further object is to so mount the movable arms that they may be folded together so as to lie longitudinally upon the main or stationary arm when the tool is not in use, thus to be easily stored in a box or carried in a pocket.

Another object is to provide a tool in which the movable arms can be quickly and securely held at right angles to each other.

Another obj ect isto provide a stop for limiting the movement of the movable arms when one of them is brought to position at right angles to the main or stationary arm.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that, within the scope of what is claimed, changes in the precise embodiment of the invention shown can be made without departing from the spirit of the invention.

In the accompanying drawings the preferred form of the invention has been shown.

In said drawings- Figure 1 is a plan view of a portion of the tool with the parts set up for use.

Fig. 2 is a similar View showing the tool f lded.

Specification of Letters Patent.

Patented Oct. 18, 1921.

Serial No. 434,613.

Fig. 3 is an edge view, a portion being shown in section.

Referring to the figures by characters of reference 1 designates the stationary or main arm of the tool which can be of any desired length and has two straight parallel edges adjacent which are provided graduations designating inches or any other units of measure, and fractions thereof. Secured on this arm 1 preferably near one end thereof is a segment 2 one end of which is extended slightly beyond one side edge of the arm 1 and has an inwardly extending ear 3 which laps and is secured to the arm 1, the other end of the segment being fastened directly to the arm. Formed on the segment 2 are two series of graduations extending through 90, the graduations of one series being in dicated by numerals ranging from 0 to 90 and the graduations of the other series being indicated by numerals ranging from 90 to 180, the 90 graduations of the two series coinciding and the 0 and 180 graduations likewise coinciding as will be apparent by referring to the drawings.

A combined pivot and binding screw 4 is threaded in the arm 1, the segment 2 being concentric therewith, and pivotally mounted on this screw is a movable arm 5 suitably graduated and one end of which abuts against and is slidable along the inner arouate edge of the segment 2. This end has an indicating graduation 7 or the like designed to register with any one of the graduations on the segment so that the angle at which the arm 5 is extended relative to the arm 1 can thus be determined readily.

The parts are so proportioned that when the graduation 7 alines with the graduation designated by the numeral 90, the arm 5 abuts against the ear 3 which thus acts as a stop.

Pivotally mounted on the screw 4 is another movable arm 8 suitably graduated and which has a lug 9 upstanding therefrom adapted to be detachably engaged by one end of a link 10 the other end of which is pivotally attached to the arm 5 as shown at 11. en the link 10 is in engagement with the lug 9, as shown in Fig. 1, the two arms 5 and 8 are held at right angles to each other and when the arm 5 is adjusted angularly to a desired position relative to the segment the arm 8 will likewise move therewith, thus giving at all times a line at right angles to that which might be scribed along the arm 5 and which forms with the edge of the arm 1 an angle which, when added to, that formedbetwecn the arms 1 and 5 will equal a right angle.

When the tool is not in use the link 10 can be sprung out of engagement with the lug 9 and the arms 5 and 8 swung together so as to lie parallel with each other and with the arm 1 as shown in Fig. 2.

This tool can be used for all of the purposes for which any tool of a similar character can be used, such as laying off theend cuts of rafters, laying out braces, stair horses, etc., as will be apparent to those skilled in the art.

What is claimed is 7 1. A geometrical tool comprising a main arm, a graduated segment secured thereon and having an'end stop, pivotally connected 2. A geometrical tool including a main arm, a graduated se ment mounted thereon, V

movable arms, means for pivotally connecting said arms together and to the main arm and for holding them against relative movement, one of the movable arms abutting against and being shiftable along the inner edge of the segment and carrying an in dex, and means extending between the pivot of the arms and the segment for maintaining the movable arms at a predetermined angle relative to each other during the movement thereof relative to the main arm, said means being shiftable to permit folding of the movable arms.

3. A geometrical tool including'a main arm, a segment extending over one face thereof and having a terminal stop, superposed movable arms, a combined pivot and clamping screw engaging all of the arms, one ot'said arms being movable along one edge, of the segment and against the stop and the other movable arm being movable across thesegment and past the stop, and a brace carried by one of the movable arms and detachably engaging the other movable arm for holding said arms normally at right angles to each other.

In testimony that I claim the foregoing asrmy own, I have hereto afiixed my signa-.

ture in the presence of two witnesses.

JAMESVH. ROBERTS.

Witnesses;

IVY E. SIMPSON, 'Ae ns RooKnLL'r. 

